1. Field of the Invention
The present technique relates generally to assembling a number of components, such as engine components. More specifically, the present technique relates to a system and method for identifying characteristics of an engine component, such as a fuel injector, and configuring a control system for an engine to account for performance characteristics of the component.
2. Description of the Related Art
In fuel injected engines, it is generally considered desirable that each injector deliver approximately the same quantity of fuel in approximately the same timed relationship to the engine for proper operation. It is well known that problems arise when the performance, and more particularly the timing and the quantity of fuel delivered by the injectors, diverge from target values beyond acceptable limits. For example, injector performance deviation or variability will cause different torques to be generated between cylinders due to unequal fuel amounts being injected, or from the relative timing of such fuel injection. Further, knowledge that such variations occur requires engine system designers to account for this variability by designing an engine system to provide an output equal to the maximum theoretical output less an amount due to the worse case fuel injector variability, rather than design a system for peak or maximum cylinder pressures or output.
Various attempts have been made for solving these problems associated with fuel injectors. One straightforward approach is simply to adhere to rigid manufacturing and test procedures to assure each injector meets a rigid desired design specification. This is a common approach for replacement fuel injectors. To simplify the service process, a set of service injector coefficient data may be reprogrammed in an Electronic Control Unit (ECU) memory and all service injectors manufactured under stringent tolerance requirements so as to function with the known service coefficients. In this manner, whenever a fuel injector fails, one of the special service fuel injectors is installed, and the ECU is simply instructed to use the service coefficient data for that particular cylinder. While this approach results in satisfactory operating conditions, it is relatively costly. That is, to manufacture each service injector with such stringent tolerances so that the flow rate satisfies a desired performance dictated by the fixed service injector coefficient data, results in a relatively expensive replacement fuel injector. Therefore, this approach is undesirable for both initial assembly and later servicing due to the increased manufacturing and assembly costs, and the low yield of acceptable units.
Sophisticated electronic equipment and control have made it possible to better control the problem of timing and delivery variations of similar fuel injectors. One such control involves compensating for individual injector variations and includes an electronic control module having a memory for storing compensation signals for each injector. The compensation signals are generally derived from a limited number of operating conditions, because fuel injectors may have relatively predictable, although different, performance characteristics. Therefore, the electronic control module can adjust the base fuel delivery signal for each injector as a function of the compensation data signal for that injector with relatively good results.
Unfortunately, some of the more complex and advanced fuel injectors now being manufactured do not follow readily predictable fuel-flow characteristics with increased pulse-width inputs, as was the case with earlier style injectors. Consequently, unless individual compensation signals are determined for an extremely large number of operating points resulting from different pulse widths, such systems would not operate satisfactorily with those advanced fuel injectors. Also, the amount of memory needed to store a sufficiently large number of compensation signals covering the fall range of fuel injector operation would be excessively large, and the cost involved in the necessary testing to determine such a large number of compensation signals would be unacceptable.
Advanced fuel injectors are very complicated and difficult to manufacture. Therefore, it is very difficult to provide consistent operating characteristics between injectors, even though they are intended to be substantially identical. Furthermore, although varying the pulse width of a control signal may be used to vary the amount of fuel an injector provides to a cylinder (hereinafter referred to as fuel flow or flow rate), a performance curve of these complicated fuel injectors (fuel flow vs. pulse width) cannot be accurately defined by a second-order polynomial as can some older types of fuel injectors. Consequently, determining the pulse width for a desired RPM by extrapolating between sample data points does not provide satisfactory performance.
Accordingly, it would be desirable to provide a system and method for optimizing a combustion engine for a production fuel injector having normal or wide tolerances, thereby lowering costs and manufacturing difficulties. Specifically, it would be desirable to have performance characteristics for a particular fuel injector readily available and electronically transferable, such that the particular fuel injector could be readily assembled into a combustion engine for substantially optimal performance therein. Similarly, it would be desirable to have such performance characteristics readily available and electronically transferable for other components of a combustion engine system. Moreover, it would be desirable to provide such a technique that could be used with other engine components and systems, as well as with other types of machines and systems.